1. Technical Field
The present invention relates to a liquid jet head which jets a liquid droplet onto a recording medium to perform recording thereon, and to a liquid jet apparatus.
2. Related Art
In recent years, there is used a liquid jet head which employs an ink jet method to record a character and/or a figure on a sheet of recording paper or the like by ejecting thereon an ink droplet, or to form a functional thin film on a surface of an element substrate by ejecting thereon a liquid material. In this method, liquid such as ink or the liquid material is guided from a liquid tank to a channel through a supply tube so that the liquid filling the channel is pressurized and ejected from a nozzle communicating with the channel. The liquid is ejected to record a character and/or a figure or form a functional thin film having a predetermined shape by moving a liquid jet head and/or a recording medium.
A liquid jet head of this type is described in JP 2012-101437 A. FIG. 8 is an exploded perspective view of the liquid jet head described in JP 2012-101437 A. A liquid jet head 201 includes a piezoelectric body substrate 202, a cover plate 203 bonded to a surface SF of the piezoelectric body substrate 202, and a nozzle plate 216 bonded to a front end FE of the piezoelectric body substrate 202. A dummy channel 212 and an ejection channel 211 are alternately arrayed on the surface SF of the piezoelectric body substrate 202. The cover plate 203 includes a liquid supply chamber 214 and a slit 215 which only communicates with the ejection channel 211 but does not communicate with the dummy channel 212. The nozzle plate 216 includes a nozzle 217, which communicates with the ejection channel 211 opened on the front end FE. The ejection channel 211 and the dummy channel 212 are separated by a partition 206, and a drive electrode 207 is formed on a side surface of the partition 206. The drive electrode 207 is electrically connected to an electrode terminal formed on the surface SF of the piezoelectric body substrate 202 in the vicinity of a rear end RE thereof. A flexible circuit board 204 is connected to the surface SF in the vicinity of the rear end RE so that a drive signal is supplied from outside. Liquid supplied to the liquid supply chamber 214 flows into the ejection channel 211 through the slit 215. The partition 206 is deformed when the drive signal is supplied to the drive electrode 207, thereby causing the capacity of the ejection channel 211 to change abruptly and causing the liquid droplet to be ejected from the nozzle 217.
Described in JP 2003-505281 W is a liquid jet head of a through-flow type in which liquid within a channel circulates. The through-flow type can promptly discharge air bubbles and/or a foreign matter mixed in the liquid out of the channel. As a result, maintenance can be carried out without using a cap structure or a service station, whereby the liquid is consumed less at the time of the maintenance to be able to keep down a running cost. Moreover, the wasteful consumption of a recording medium caused by defective ejection can be kept to the minimum.
FIG. 9 is an exploded perspective view of the liquid jet head described in JP 2003-505281 W. The liquid jet head includes: PZT wafers 88 and 89 formed of two piezoelectric elements stacked together to construct flow paths 90, 92, and 94; a mask plate 100 on which an opening that communicates with each of the flow paths 90 and 94 is formed but which blocks the flow path 92; an opening plate 66 on which an opening portion is formed to bring the flow path 90 in communication with the flow path 94 while striding over the flow path 92; and a nozzle plate 64 on which a nozzle 102 communicating with the opening portion on the opening plate 66 is formed. Liquid flows from the flow path 90 to the flow path 94 through the opening portion formed on the opening plate 66, as indicated by arrow 52. In other words, the liquid circulates around the flow path 92. A line electrode is provided on a side surface of each of two walls 96 and 98 facing the flow path 92 while an earth electrode is provided on a side surface of each of the walls facing the flow paths 90 and 94, so that the walls 96 and 98 are driven by these electrodes to eject small liquid droplets from the nozzle 102.
The groove width and groove interval of the ejection channel 211 and the dummy channel 212 have been getting narrower, down to 100 μm to 20 μm, in recent years. It is thus required to align the nozzle 217 on the nozzle plate 216 and the ejection channel 211 opened at the front end FE with high precision in the liquid jet head described in JP 2012-101437 A, for example. It is difficult to accurately perform the alignment especially when an opaque material such as a metal plate is used as the nozzle plate 216, because the ejection channel 211 is not visible through the nozzle plate 216 when the nozzle plate 216 is to be bonded to the front end FE. The positioning accuracy decreases when the nozzle plate 216 and the piezoelectric body substrate 202 are aligned by using the outer shape as a reference, for example. When attempting to align the nozzle 217 with the ejection channel 211 opened at the front end FE through the nozzle, one cannot distinguish whether the opening visible through the nozzle 217 is the opening of the ejection channel 211 or the opening of the dummy channel 212.
A similar problem can also occur when installing the cover plate 203 onto the ejection channel 211 formed on the surface SF of the piezoelectric body substrate 202. The cover plate 203 normally being opaque, the ejection channel 211 and the dummy channel 212 are not visible through the cover plate 203 when bonding the cover plate to the surface SF. Now, when attempting to perform the alignment with a groove seen through the slit 215, one cannot always distinguish whether the groove seen through the slit 215 is the ejection channel 211 or the dummy channel 212.
Moreover, the liquid jet head described in JP 2003-505281 W is formed of many components including the mask plate 100, the opening plate 66, and the nozzle plate 64 to circulate liquid, so that it gets extremely complex to align each plate. It is difficult to perform the alignment with high precision when one attempts to adhere these components to the PZT wafers 88 and 89 by using the outer shape as a reference.